Method for producing a measuring transducer

ABSTRACT

A method is provided for producing a measuring transducer in order to transform at least one physical variable into at least one electric variable. A plurality of planar, insulating and conductive layers are respectively structured according to predefineable models which are adapted to each other and which are assembled in order to form a multi-layered arrangement.

The invention relates to a method for producing a measuring transducerfor converting at least one physical quantity into at least oneelectrical quantity.

Such measuring transducers for converting physical quantities such aspressure, temperature, flow rate or the like into an electricalquantities such as voltage, current or pulse sequence are known fromprior use and relevant publications.

The known measuring transducers are characterized by an elaboratemulti-part and specialized structure, which is produced by miscellaneousassembly technologies.

It is therefore an object of the invention to simplify the production ofmeasuring transducers.

The invention is based on a measuring transducer having at least onesensor for converting at least one physical quantity into at least oneelectrical quantity.

The essence of the invention consists in a planar multi-layeredarrangement consisting of insulating layers and conductive layersinsulated from one another, which are respectively structured accordingto predetermined patterns matched to one another, and are assembled toform a multi-layered arrangement. Starting with a first layer, furtherlayers are successively stacked on. Finally, the stack is assembled bypressure application.

This process is known in principle for producing multi-layered circuitboards as support elements for electronic components in printedcircuits, but it has surprisingly been shown that the carrier materialknown per se is suitable as a functional element in a measuringtransducer, so that the production process is reduced to a fewtechnologically well-controlled steps.

According to one feature of the invention, the patterns are recessedinto the insulating and/or conductive layers. In the case of patternsmatched to one another in successive layers, recesses are thereby formedin which a sensor and electrical circuit elements can be fitted.

According to another feature of the invention, the patterns areimpressed into the insulating and/or conductive layers. In this way,channels are formed through which a process medium can be fed to thesensor.

While the aforementioned patterning is based respectively on materialremoval and material displacement, according to another feature of theinvention the patterns of the insulating and/or conductive layers aregrown. In the context of this disclosure, this is intended to mean anyform of pattern-forming material growth in a layer. In particular thelayer thicknesses of interconnections, i.e. patterned conductive layers,are amplified in this way.

The starting point of the multi-layered arrangement is a circuit boardknown per se, consisting of a supporting insulator layer and at leastone conductive layer structured in the form of interconnectionsaccording to predetermined patterns. This circuit board is equipped withone or more sensor elements and further electrical circuit elements, asa function of the type of measuring transducer. The electricalconnection between the electrical circuit elements and the sensorelements is formed by at least one patterned conductive layer.

The circuit board consists of a resin-impregnated support material,which is coated on one or both sides with a copper foil. As a functionof the type of electrical circuit elements and sensor elements, they areconnected suitably to the patterned copper foil. This includes inparticular, but not exclusively, soldering and bonding.

Further equivalent insulating layers and conductive layers insulatedfrom one another are stacked on at least one side of this circuit board.The successive layers are assembled together with the interposition ofan adhesion promoter and by pressure application. In particular but notexclusively, so-called prepregs i.e. composite films consisting of asupport material and a hot-curing epoxy resin as binder, are provided asa bonding agent.

According to one feature of the invention, as a function of the type ofmeasuring transducer, at least one measuring transducer-specificequipment element is inserted between two successive assembly steps.These include in particular, but not exclusively, capillaries forfilling the sensor space with a measuring transducer-specific medium.

These measures lead to a measuring transducer which is made according toa uniform production process by employing technologically simple,technically introduced processes.

Advantageously, the constituents of the package of the sensor and of theelectrical circuit elements, the support elements for the electricalcircuit elements including the electrical connection means as well asthe measuring transducer-specific equipment elements, are made from thesame material combination and are assembled according to a uniformmethod.

Supporting and functional elements are particularly advantageouslycombined in the same component. This component is produced by atechnologically undemanding process known per se.

Other details and advantages of the invention will be explained in moredetail below with reference to the example of a differential pressuremeasuring transducer unit in several embodiments. In the requisitedrawings:

FIG. 1 shows a sectional representation of a first embodiment of adifferential pressure measuring transducer unit

FIG. 2 shows a sectional representation of a second embodiment of adifferential pressure measuring transducer unit

FIG. 3 shows a sectional representation of a third embodiment of adifferential pressure measuring transducer unit

FIG. 4 shows a sectional representation of a differential pressuremeasuring transducer

FIG. 1 shows a sectional representation of the essential constituents ofa differential pressure measuring transducer unit in a first embodiment.The differential pressure measuring transducer unit consists essentiallyof a stack of insulating layers 21 to 25 and conductive layers 11 to 15insulated from one another, which partially comprise recesses 31 to 37patterned to match one another and overlapping one another, into which asensor 60 and further electrical circuit elements, such as measuredvalue processing means, 80 are fitted.

In this embodiment, the insulating layer 21 comprises two identicalfunnel-shaped recesses 31 and 32. The outside of the insulating layer 21is covered by the conductive layer 11, which is configured as aseparating membrane 51 and 52 in the region of the recesses 31 and 32.The separating membranes 51 and 52 are preferably embossed in the formof concentric corrugated pattern known per se. The process pressures acton the other side of the separating membranes 51 and 52 from theinsulating layer 21.

The insulating layers 22 and 24 separated from one another by theinsulating layer 23 are patterned to match one another and comprisecongruent recesses 33 and 34. In the overlap region of the recesses 33and 34, the insulating layer 23 is configured as a membrane 50. Therecess 33 is connected to the funnel-shaped recess 32 via a channel 42.The recess 34 is connected to the funnel-shaped recess 31 via a channel41.

The insulating layers 23 and 24 as well as the conductive layer 14furthermore comprise partially overlapping recesses 35 and 36, intowhich the sensor 60 is fitted. The sensor 60 is connectedpressure-tightly to the insulating layer 24. The conductive layer 14 ispatterned with openings. The sensor 60 comprises electrical terminals,which are connected via bonding connections 70 to various patterns ofthe conductive layer 14. The recess 35 is connected via theaforementioned channel 41 to the funnel-shaped recess 31 and the recess34. The recess 36 is connected via a channel 43 to the recess 33 and incontinuation via the channel 42 to the funnel-shaped recess 32.

The channels 41 to 43 are configured as recesses of the conductivelayers 13 and 14 arranged between the insulating layers 22, 23 and 24.

The membrane 50 and the recesses 33 and 34 constitute the overloadsystem of the differential pressure measuring transducer unit. Thedifference in the process pressure acting on the separating membranes 51and 52 deflects the separating membranes 51 and 52 while increasing ordecreasing the free volumes of the recesses 33 and 34. The volumedifference is equalized via the channels 41 to 43 into the sensorchambers 35 and 36 and the recesses 33 and 34. In the event of anoverload, the membrane 50 is deflected pressure-dependently.

The insulating layers 22 and 23 as well as the conductive layer 13furthermore comprise overlapping recesses 37, into which the measuredvalue processing means 80 are fitted. In this embodiment, the recess 37is closed on all sides so that the measured value processing means 80are embedded while being protected against mechanical damage. Themeasured value processing means 80 are electrically and mechanicallyconnected to track-shaped patterns of the conductive layer 14.

The conductive layers 12 and 15, arranged between the insulating layers21 and 22 as well as 24 and 25, are designed as shielding surfaces forshielding the sensor 60 and the measured value processing means 80 fromelectromagnetic radiation.

In particular, it is proposed that the conductive layers 12 to 15 shouldconsist of copper and the insulating layers 21 to 25 should consist offiber-reinforced synthetic resin. For the conductive layer 11, stainlesssteel is preferred.

Starting with a base circuit board consisting of the insulating layer 24and the conductive layer 14, during the production of the differentialpressure measuring transducer unit, further insulating and conductivelayers are applied according to the structure described above with theinterposition of an adhesion promoter, and the entire stack ishot-pressed together.

In a preferred embodiment an adhesive film known per se, consisting ofsynthetic resin, is provided as the adhesion promoter. As analternative, it may be proposed for the differential pressure measuringtransducer unit to be constructed from a stack of synthetic resin platescovered with copper on both sides, and for solder to be provided as theadhesion promoter.

The recesses 31 to 36 as well as the channels 41 to 43 are filled with asubstantially incompressible fluid, in particular silicone oil. Thefluid is introduced into the cavities via capillaries 53 and 54represented in FIG. 3. After filling, the capillaries 53 and 54 areclosed pressure-tightly.

Using the same references for means which are the same, FIG. 2 shows asecond embodiment of the differential pressure measuring transducer unitaccording to the invention. The differential pressure measuringtransducer unit consists essentially of a stack of insulating layers 21to 25 and conductive layers 11 to 16 insulated from one another, whichpartially comprise patterns matched to one another with overlappingrecesses 31 to 37, into which a sensor 60 and measured value processingmeans 80 are fitted.

In this second embodiment, the insulating layers 21 and 25 respectivelycomprise a funnel-shaped recess 31 and 32 which lie symmetricallyopposite. The outside of the insulating layer 21 is covered by theconductive layer 11 and the outside of the insulating layer 25 iscovered by the conductive layer 16. In the region of the recesses 31 and32, the conductive layers 11 and 16 are configured as a separatingmembrane 51 and 52. The separating membranes 51 and 52 are preferablyembossed in the form of a concentric corrugated pattern known per se.The process pressures act on the other side of the separating membrane51 from the insulating layer 21 and on the other side of the separatingmembrane 52 from the insulating layer 25.

The insulating layers 22 and 24 separated from one another by theinsulating layer 23 comprise congruent recesses 33 and 34. In theoverlap region of the recesses 33 and 34, the insulating layer 23 isconfigured as a membrane 50. The recess 33 is connected to thefunnel-shaped recess 32. The recess 34 is connected to the funnel-shapedrecess 31.

The insulating layers 23 and 24 as well as the conductive layer 14furthermore comprise partially overlapping recesses 35 and 36, intowhich the sensor 60 is fitted. The sensor 60 is connectedpressure-tightly to the insulating layer 24. The conductive layer 14 ispatterned with openings. The sensor 60 comprises electrical terminals,which are connected via bonding connections 70 to various patterns ofthe conductive layer 14. The recess 35 is connected via a channel 41 tothe recess 34 and in continuation to the funnel-shaped recesses 31. Therecess 36 is connected via a channel 43 to the recess 33 and incontinuation to the funnel-shaped recess 32.

The channels 41 and 43 are configured as recesses of the conductivelayers 13 and 15 arranged between the insulating layers 22 and 23 aswell as 24 and 25.

The membrane 50 and the recesses 33 and 34 constitute the overloadsystem of the differential pressure measuring transducer unit. Thedifference in the process pressure acting on the separating membranes 51and 52 deflects the separating membranes 51 and 52 while increasing ordecreasing the free volumes of the recesses 33 and 34. The volumedifference is equalized into the recesses 33 and 34 and via the channels41 and 43 into the sensor chambers 35 and 36. In the event of anoverload, the membrane 50 is deflected pressure-dependently.

The insulating layers 21, 22 and 23 as well as the conductive layers 11,12 and 13 furthermore comprise overlapping recesses 37, into which themeasured value processing means 80 are fitted. In this embodiment, therecess 37 is open on one side so that the measured value processingmeans 80 are accessible but still embedded while being substantiallyprotected against mechanical damage. The measured value processing means80 are electrically and mechanically connected to track-shaped patternsof the conductive layer 14.

The conductive layers 12 and 15, arranged between the insulating layers21 and 22 as well as 24 and 25, are designed as shielding surfaces forshielding the sensor 60 and the measured value processing means 80 fromelectromagnetic radiation.

In particular, it is proposed that the conductive layers 12 to 15 shouldconsist of copper and the insulating layers 21 to 25 should consist offiber-reinforced synthetic resin. For the conductive layers 11 and 16,stainless steel is preferred.

Starting with a base circuit board consisting of the insulating layer 24and the conductive layer 14, during the production of the differentialpressure measuring transducer unit, further insulating and conductivelayers are applied according to the structure described above with theinterposition of an adhesion promoter, and the entire stack ishot-pressed together.

In a preferred embodiment an adhesive film known per se, consisting ofsynthetic resin, is provided as the adhesion promoter. As analternative, it may be proposed for the differential pressure measuringtransducer unit to be constructed from a stack of synthetic resin platescovered with copper on both sides, and for solder to be provided as theadhesion promoter.

The recesses 31 to 36 as well as the channels 41 to 43 are filled with asubstantially incompressible fluid, in particular silicone oil. Thefluid is introduced into the cavities via capillaries 53 and 54represented in FIG. 3. After filling, the capillaries 53 and 54 areclosed pressure-tightly.

Using the same references for means which are the same. FIG. 3 shows athird embodiment of the differential pressure measuring transducer unitaccording to the invention. The differential pressure measuringtransducer unit in this third embodiment also consists essentially of astack of insulating layers 21 to 26 and conductive layers 11 to 16insulated from one another, which partially comprise patterns matched toone another with overlapping recesses 31 to 37, into which a sensor 60and measured value processing means 80 are fitted.

In this third embodiment, the insulating layers 21 and 25 respectivelycomprise a funnel-shaped recess 31 and 32 which lie symmetricallyopposite. The outside of the insulating layer 21 is covered by theconductive layer 11 and the outside of the insulating layer 25 iscovered by the conductive layer 16. In the region of the recesses 31 and32, the conductive layers 11 and 16 are configured as a separatingmembrane 51 and 52. The separating membranes 51 and 52 are preferablyembossed in the form of a concentric corrugated pattern known per se.The process pressures act on the other side of the separating membrane51 from the insulating layer 21 and on the other side of the separatingmembrane 52 from the insulating layer 25.

The insulating layers 22 and 24 separated from one another by theconductive layer 17, as well as the insulating layer 26 and theconductive layer 14, comprise congruent recesses 33 and 34. In theoverlap region of the recesses 33 and 34, the conductive layer 17 isconfigured as a membrane 50. The recess 33 is connected to thefunnel-shaped recess 32. The recess 34 is connected to the funnel-shapedrecess 31.

The insulating layers 24 and 26 as well as the conductive layer 14furthermore comprise partially overlapping recesses 35 and 36, intowhich the sensor 60 is fitted. The sensor 60 is connectedpressure-tightly to the insulating layer 24. The conductive layer 14 ispatterned with openings. The sensor 60 comprises electrical terminals,which are connected via bonding connections 70 to various patterns ofthe conductive layer 14. The recess 35 is connected via a channel 41 tothe recess 34 and in continuation to the funnel-shaped recesses 31. Therecess 36 is connected via a channel 43 to the recess 33 and incontinuation to the funnel-shaped recess 32.

The channels 41 and 43 are configured as recesses in the insulatinglayers 22 and 26. The channel-forming recesses are preferably impressedinto the insulating layers 22 and 26.

The membrane 50 and the recesses 33 and 34 constitute the overloadsystem of the differential pressure measuring transducer unit. Thedifference in the process pressure acting on the separating membranes 51and 52 deflects the separating membranes 51 and 52 while increasing ordecreasing the free volumes of the recesses 33 and 34. The volumedifference is equalized into the recesses 33 and 34 and via the channels41 and 43 into the sensor chambers 35 and 36. In the event of anoverload, the membrane 50 is deflected pressure-dependently.

The insulating layers 25 and 26 as well as the conductive layer 16furthermore comprise overlapping recesses 37, into which the measuredvalue processing means 80 are fitted. In this embodiment, the recess 37is open on one side so that the measured value processing means 80 areaccessible but still embedded while being substantially protectedagainst mechanical damage. The measured value processing means 80 areelectrically and mechanically connected to track-shaped patterns of theconductive layer 14.

The conductive layer 17, arranged between the insulating layers 22 and24, is designed as a shielding surface for shielding the sensor 60 andthe measured value processing means 80 from electromagnetic radiation.

A recess 38 is furthermore provided, which in this third embodiment isarranged congruently in the insulating layers 22 and 24 to 26 as well asin the conductive layers 14, 16 and 17. The ends of two capillaries 53and 54, the opposite ends of which respectively extend into the recesses33 and 34, are fitted as measuring transducer-specific equipmentelements in this recess 38.

In particular, it is proposed that the conductive layers 14 and 17should consist of copper and the insulating layers 21 to 26 shouldconsist of fiber-reinforced synthetic resin. For the conductive layers11 and 16, stainless steel is preferred.

Starting with a base circuit board consisting of the insulating layer 24and the conductive layer 14, during the production of the differentialpressure measuring transducer unit, further insulating and conductivelayers are applied according to the structure described above with theinterposition of an adhesion promoter, and the entire stack ishot-pressed together.

Irrespective of the embodiment, before the insulating layer 21 isapplied, the capillary 53 is introduced so that the one tube endprojects into the recess 34 and the other tube end projects into therecess 38. Before the insulating layer 25 is applied, the capillary 54is introduced so that one tube end projects into the recess 33 and theother tube end projects into the recess 38.

In a preferred embodiment an adhesive film known per se, consisting ofsynthetic resin, is provided as the adhesion promoter.

The recesses 31 to 36 as well as the channels 41 and 43 are filled witha substantially incompressible fluid, in particular silicone oil. Thefluid is introduced into the cavities via capillaries 53 and 54. Afterfilling, the capillaries 53 and 54 are closed pressure-tightly.

Lastly, FIG. 4 shows a sectional representation of a differentialpressure measuring transducer having a differential pressure measuringtransducer unit according to FIG. 2. In this case, the differentialpressure measuring transducer unit is clamped between two flange caps90, which bear on the outer conductive layers 11 and 16.

Each flange cap 90 comprises a bore 91 whose opening that faces awayfrom the differential pressure measuring transducer unit is equippedwith a flange appendage 92. The bore 91 in the flange cap 90 is arrangedin the region of the separating membranes 51 and 52 of the differentialpressure measuring transducer unit. Each bore 91 in the flange cap 90 isassigned two threaded bores 93, which are configured as blind bores.

The flange caps 90 are screwed together by a multiplicity of bolts 95,which are distributed uniformly over the circumference of thedifferential pressure measuring transducer unit. To this end, one of theflange caps 90 comprises bores and the opposite flange cap 90 comprisescorresponding threaded bores.

For correct use of the differential pressure measuring transducer, animpulse line is attached to each flange cap 90. The impulse linesrespectively comprise a flange-like collar, which is held by means of aunion plate in the flange appendage 92. The union plate is fastened onthe flange cap 90 by screws, which engage into the threaded bores 93.

LIST OF REFERENCES

-   11 to 17 conductive layer-   21 to 26 insulating layer-   31 to 38 recess-   41 to 43 channel-   50 membrane-   51, 52 separating membrane-   53, 54 capillary-   60 sensor-   70 bonding connection-   80 measured value processing means-   90 flange cap-   91 bore-   92 flange appendage-   93 threaded bore-   95 bolt

1. A method for producing a measuring transducer configured to convertat least one physical quantity into at least one electrical quantity,the method comprising: structuring a multiplicity of planar insulatinglayers and conductive layers in an alternating order so that, in atleast one pair of adjacent insulating and conductive layers among thestructured layers, corresponding patterns respectively formed in eachone of the adjacent insulating and conductive layers of the at least onepair are matched to one another when the adjacent insulating andconductive layers of the at least one pair are structured in thealternating order; and assembling the structured insulating layers andconductive layers to form a multi-layered arrangement in which thecorresponding patterns respectively formed in each one of the adjacentlystructured insulating and conductive layers of the at least one pair arematched to one another while the adjacently structured insulating andconductive layers of the at least one pair are assembled in thealternating order in the multi-layered arrangement.
 2. The method asclaimed in claim 1, wherein the patterns are impressed into theinsulating and/or conductive layers.
 3. The method as claimed in claim1, wherein the patterns are recessed into the insulating and/orconductive layers.
 4. The method as claimed in claim 1, wherein thepatterns of the insulating and/or conductive layers are grown.
 5. Themethod as claimed in claim 1, wherein the insulating and/or conductivelayers of the multi-layered arrangement are assembled together with theinterposition of an adhesion promoter and by pressure application. 6.The method as claimed in claim 1, wherein the insulating and/orconductive layers of the multi-layered arrangement are assembled in aplurality of steps, at least one of the insulating and conductive layersbeing fitted with electrical circuit elements between two successiveassembly steps.
 7. The method as claimed in claim 6, wherein at leastone measuring transducer-specific equipment element is inserted betweentwo successive assembly steps.
 8. The method as claimed in claim 4,wherein the insulating and/or conductive layers of the multi-layeredarrangement are assembled together with the interposition of an adhesionpromoter and by pressure application.
 9. The method as claimed in claim5, wherein the insulating and/or conductive layers of the multi-layeredarrangement are assembled in a plurality of steps, at least one of theinsulating and conductive layers being fitted with electrical circuitelements between two successive assembly steps.
 10. A method forproducing a measuring transducer, comprising: arranging a plurality ofplanar insulating layers and conductive layers in an alternating orderso that, in at least one pair of adjacent insulating and conductivelayers among the arranged layers, corresponding patterns respectivelyformed in each one of the adjacent insulating and conductive layers ofthe at least one pair are matched to one another when the adjacentinsulating and conductive layers of the at least one pair are arrangedin the alternating order; and forming a measuring transducer based on amulti-layered arrangement of the plurality of planar insulating andconductive layers, in which the corresponding patterns respectivelyformed in each one of the adjacently arranged insulating and conductivelayers of the at least one pair are matched to one another while theadjacently arranged insulating and conductive layers of the at least onepair are arranged in the alternating order in the multi-layeredarrangement, wherein the measuring transducer is capable of convertingat least one physical quantity into at least one electrical quantity.11. The method as claimed in claim 10, wherein the patterns areimpressed into the insulating and/or conductive layers.
 12. The methodas claimed in claim 10, wherein the patterns are recessed into theinsulating and/or conductive layers.
 13. The method as claimed in claim10, wherein the patterns of the insulating and/or conductive layers aregrown.
 14. The method as claimed in claim 10, wherein the insulatingand/or conductive layers of the multi-layered arrangement are assembledtogether with the interposition of an adhesion promoter and by pressureapplication.
 15. The method as claimed in claim 10, wherein theinsulating and/or conductive layers of the multi-layered arrangement areassembled in a plurality of steps, at least one of the insulating andconductive layers being fitted with electrical circuit elements betweentwo successive assembly steps.
 16. The method as claimed in claim 15,wherein at least one measuring transducer-specific equipment element isinserted between two successive assembly steps.
 17. The method asclaimed in claim 13, wherein the insulating and/or conductive layers ofthe multi-layered arrangement are assembled together with theinterposition of an adhesion promoter and by pressure application. 18.The method as claimed in claim 14, wherein the insulating and/orconductive layers of the multi-layered arrangement are assembled in aplurality of steps, at least one of the insulating and conductive layersbeing fitted with electrical circuit elements between two successiveassembly steps.